Nanopatterned substrate serving as both a current collector and template for nanostructured electrode growth

ABSTRACT

A process of forming and the resulting nano-pitted metal substrate that serves both as patterns to grow nanostructured materials and as current collectors for the resulting nanostructured material is disclosed herein. The nano-pitted substrate can be fabricated from any suitable conductive material that allows nanostructured electrodes to be grown directly on the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a continuation-in-part ofU.S. patent application Ser. No. 12/695,835 filed Jan. 28, 2010, whichclaims priority to U.S. Provisional Patent Application Ser. No.61/148,671, filed Jan. 30, 2009, and U.S. patent application Ser. No.11/383,146 filed May 12, 2006, now U.S. Pat. No. 7,736,724 issued Jun.15, 2010, which claims priority to U.S. Provisional Patent ApplicationSer. No. 60/681,222 filed May 13, 2005, each of which is incorporatedherein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a process of forming a nano-pittedsubstrate that serves both as patterns to grow nanostructured materialsand as current collectors for the nanostructured material that has beengrown thereupon.

2. Description of the Related Art

The potential of nanotechnology to provide new technologicalbreakthroughs is the object of much current attention. Nanostructuredmaterials have the potential for enhanced properties and efficiencyimprovements in virtually every area of science and technology throughenhanced surface areas and quantum-scale reactions.

The process of nanoscale or microscale deposition of particles by asputtering process is the ejection of particles from a condensed-mattertarget due to the impingement of energetic projectile particles onto asubstrate having a plurality of holes or pores that range in diameterbetween ten (10) micrometers to one (1) nanometer (nm). Operatively, thesource of coating material, referred to as the target or substrate, ismounted opposite to the sample, in this case a porous substrate in avacuum chamber. The most common method of generating ion bombardment isto backfill the evacuated chamber with a continual flow of gas andestablishing a glow discharge, indicating that ionization is occurring.A negative potential applied to the target causes it to be bombardedwith positive-ions while the substrate is kept grounded. Impingement ofthe positive-ion projectile results in ejection of target atoms ormolecules and their deposition on the substrate.

One of the most useful characteristics of the sputtering process is itsuniversality: virtually any material is a coating candidate. Sputteringsystems assume an almost unlimited variety of configurations, dependingon the desired application. DC discharge methods are often used forsputtering metals, while an RF potential is used for less conductivematerials. Ion-beam sources can also be used. Targets may be elements,alloys, or compounds, in either doped or un-doped forms, and can beemployed simultaneously or sequentially. The substrate may beelectrically biased so that it too undergoes ion bombardment. A reactivegas may be used to introduce one of the coating constituents into thechamber, i.e. oxygen to combine with sputtered tin to form tin oxide(reactive sputtering).

A nanostructure fabricated by RF sputtering of barium strontium titanate(BST) on porous alumina substrates suggests that the sputtered materialdoes not penetrate into pores, but rather preferentially gathers alongthe continuous circular edge of pore openings. These types of sputteredmetal structure or “antidots” are not partially or complete capped, arenot layered, are formed only from metals, and are not used to assembleany type device.

Nanotubes and other nanostructures may be formed as large arrays, and inthis form are often referred to as nanoporous or mesoporous structures.“Meso-porous” tin oxide structures have been created using surfactanttemplating techniques. The resultant material, however, consists ofmaterial containing irregular nanopores averaging about two (2) nm insize, without long-range order. These nanoporous or mesoporus structurescannot be formed in large arrays of tunable pore sizes, which developwall height as well as porosity, and also cannot be partially orcompletely capped to form a nanobasket structure.

The assembly of individual nanostructured components into athree-dimensional battery system has been proposed as the means topromote ion diffusion in electrode materials by substantially increasingthe effective electrode surface area to improve energy per unit areacharacteristics and promote a high rate charge/discharge capacity. Suchfeatures should enhance general battery performance, but they are ofparticular importance for thin film batteries and nanobatteries able topower proposed micro and nano electromechanical systems (MEMS and NEMS).Recent work on three-dimensional architectures for improved performanceincludes rods or “posts” connected to a substrate, graphite meshes andfilms of cathode, electrolyte and anode materials lining microchannelsin an inert substrate.

Moreover, nanostructured electrode materials have been shown to haveenhanced electrode properties such as faster charging/dischargingproperties and higher available capacities. These electrodes have thepotential to be placed in battery configurations, especially where thinfilm construction is used. The two current collectors which areconductive material in the battery that collect electrons (on the anodeside) or disburse electrons (on the cathode side) are present. It is thecurrent collectors that serve to make contact between the devices thatbatteries power on one side and the two electrodes of the battery ontheir opposite sides.

Prior nanostructured electrode materials were grown from a substratethat is an insulating material, such as alumina. As the electrodematerial is grown on the substrate, the structure of the substrate ismaintained as the sputter coated layer becomes thicker. However, thegrowth substrate, being an insulator, cannot serve as a currentcollector. As such, in order to construct a battery, the delicatenanostructured electrode must be removed from the substrate and acurrent collector must then be connected to the delicate nanostructuredelectrode (sometimes the layer is only 500 nm thick) without damagingit. This is one of the important considerations for application ofnanoscale materials and engineering into what will result in a “realworld” sized product is how to connect the nanoscale aspects of thesystem to the macroscale.

It is therefore desirable to provide a nanopatterned substrate thatserves as both a current collector and template for nanostructuredelectrode growth.

It is further desirable to provide a process of constructing of ananostructured current collector that serves as both a current collectorand as a substrate to grow nanostructured electrode materials.

It is still further desirable to provide a nanopatterned substrate thatserves as both a current collector and template for nanostructuredelectrode growth that bridges the gap between the nanoscale environmentand the macroscale of commercial batteries.

It is yet further desirable to provide a nanopatterned substrate thatserves as both a current collector and template for nanostructuredelectrode growth for thin film batteries and nanobatteries, which wouldbe able to power proposed micro- and nano-electromechanical systems(MEMS and NEMS), or used in massive arrays in place of conventionalbatteries.

It is still yet further desirable to provide a process for manufacturingthin film batteries and nanobatteries using short, capped nanotubes,i.e., nanobaskets, electrochemical deposited directly on a nanopatternedsubstrate, which serves as both a current collector and the nanobasketgrowth template.

It is further desirable to provide a thin film battery or nanobatteryconstructed on a nano-pitted metal that serves as the growth substrateand the current collector for the electrode.

It is further desirable to provide a process of fabricating a thin filmbattery or nanobattery in which the electrode material does not have tobe removed from its growth substrate.

SUMMARY OF THE INVENTION

In general, in a first aspect, the invention relates to a method offabricating a nanostructure by forming an electrically conductivesubstrate having at least one nano-pit and then depositing at least onematerial along the nano-pit to form a nanostructure. The conductivesubstrate can include a plurality of the nano-pits, each having adiameter of from about 1 nm to about 10 micrometers. The conductivesubstrate can be constructed from a metal, metal alloy, electrolyte,superconductor, semiconductor, plasma, graphite or conductive polymer.The metal can be aluminum (Al), antimony (Sb), bismuth (Bi), boron (B),cadmium (Cd), carbon (C), cerium (Ce), chromium (Cr), cobalt (Co),copper (Cu), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium(Gd), germanium (Ge), gold (Au), graphite (C), hafnium (Hf), holmium(Ho), indium (In), iridium (Ir), iron (Fe), lanthanum (La), lutetium(Lu), magnesium (Mg), manganese (Mn), molybdenum (Mo), neodymium (Nd),nickel (Ni), niobium (Nb), palladium (Pd), platinum (Pt), praseodymium(Pr), rhenium (Re), ruthenium (Ru), samarium (Sm), selenium (Se),scandium (Sc), silver (Ag), silicon (Si), tantalum (Ta), terbium (Tb),thulium (Tm), tin (Sn), titanium (Ti), tungsten (W), vanadium (V),ytterbium (Yb), yttrium (Y), zirconium (Zr) or zinc (Zn). The metalalloy can be aluminum copper (AlCu), aluminum chromium (AlCr), aluminummagnesium (AlMg), aluminum silicon (AlSi), aluminum silver (AlAg),cerium gadolinium (CeGd), cerium samarium (CeSm), chromium silicon(CrSi), cobalt chromium (CoCr), cobalt iron (CoFe), cobalt iron boron(CoFeB), copper cobalt (CuCo), copper gallium (CuGa), copper indium(CuIn), copper nickel (CuNi), copper zirconium (CuZr), hafnium iron(HfFe), iron boron (FeB), iron carbon (FeC), iron manganese (FeMn),iridium manganese (IrMn), iridium rhenium (IrRe), indium tin (InSn),molybdenum silicon (MoSi), nickel aluminum (NiAl), nickel chromium(NiCr), nickel chromium silicon (NiCrSi), nickel iron (NiFe), nickelniobium titanium (NiNbTi), nickel titanium (NiTi), nickel vanadium(NiV), samarium cobalt (SmCo), silver copper (AgCu), silver tin (AgSn),tantalum aluminum (TaAl), terbium dysprosium iron (TbDyFe), terbium ironalloy (TbFe), titanium aluminum (TiAl), titanium nickel (TiNi), titaniumchromium (TiCr), tungsten rhenium (WRe), tungsten titanium (WTi),zirconium aluminum (ZrAl), zirconium iron (ZrFe), zirconium nickel(ZrNi), zirconium niobium (ZrNb), zirconium titanium (ZrTi), zirconiumyttrium (ZrY), zinc aluminum (ZnAl) or zinc magnesium (ZnMg).

The material can be deposited by sputter-coating, chemical vapordeposition or pulsed laser method, such as direct currentsputter-coating, radio frequency sputter-coating, magnetronsputter-coating or reactive sputter-coating. The material deposited canbe an oxide, polymeric, ceramic, mineral or metallic material, such ascarbon, silicon, graphite, a copper oxide, a metal alloy, a mixed metaloxide, a lithium-containing oxide, a phosphate, a fluorophosphate, asilicate, tin oxide, zinc oxide, titanium oxide, titanium dioxide,vanadium pentoxide, magnesium oxide, silicon dioxide, nichrome,hydroxyapatite, tin oxide (SnO₂), lithium cobalt oxide (LiCoO₂), zincoxide, copper oxide, titanium oxide, titanium dioxide, vanadiumpentoxide, magnesium oxide, silicon dioxide, nichrome, Li₄Ti₅O₁₂,Li₄Ti₅O₁₂, LiNixCO₁ _(_) _(2x)MnO₂, LiNi_(0.5)Mn_(1.5)O₄,Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂, LiMn₂O₄, iron olivine (LiFePO₄),LiFe_(1-x)MgPO₄, LiMoPO₄, LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃, LiVOPO₄,LiMP₂O₇, LiFe_(1.5)P₂O₇, LiVPO₄F, LiAlPO₄F, Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂,Li₂COPO₄F, Li₂NiPO₄F, Li₂FeSiO₄, Li₂MnSiO₄ or Li₂VOSiO₄.

In addition, at least one additional material may be deposited to form alayered nanostructure. The material can be deposited directly along thenano-pit to form the nanostructure, and the nanostructure can be ananostructured electrode where the conductive substrate serves as bothcurrent collector and growth substrate for the nanostructure electrode.The conductive substrate can be formed using laser ablation, a chemicaletching process, an electrochemical process, track etching, micro- ornano-lithography, contact lithography, X-ray-beam lithography,electron-beam lithography, ion-beam lithography, photo-lithography,nano-imprint lithography or chemical self-assembly.

In general, in a second aspect, the invention relates to a method forfabricating a nano-pitted substrate. The method can be accomplished bychemically polishing a metal thin film in a first acid, such asphosphoric acid, for a predetermined amount of polishing time, such asapproximately five minutes, and then oxidizing the metal thin film withan acidic solution, such as an oxalic acid electrolyte solution, in anelectrochemical cell at a predetermined temperature, such asapproximately four degrees Celsius, a first predetermined voltagepotential, such as approximately forty volts, and for a predeterminedamount of oxidation time, such as approximately one hour. Subsequently,the first predetermined voltage potential is decreased at apredetermined step-down rate, such as approximately two volts perminute, to a second predetermined voltage potential, such asapproximately two volts. Lastly, the oxidized metal thin film is etchedwith a second acid, such as phosphoric acid, to form the nano-pittedsubstrate.

In general, in a third aspect, the invention relates to a method ofconstructing a nanobattery. The method includes forming a nanostructuredanode electrode on a nano-pitted anode substrate, forming ananostructured cathode electrode on a nano-pitted cathode substrate andforming an electrolyte layer intermediate of the nanostructured anodecathode and the nanostructured anode to construct the nanobattery. Thenano-pitted anode substrate and the cathode substrate respectively serveas both a current collector and a growth substrate for thenanostructured electrode.

The anode substrate and/or the cathode substrate is constructed by laserablation, a chemical etching process, an electrochemical process, tracketching, micro- or nano-lithography, contact lithography, X-ray-beamlithography, electron-beam lithography, ion-beam lithography,photo-lithography, nano-imprint lithography or chemical self-assemblyfrom a metal, metal alloy, electrolyte, superconductor, semiconductor,plasma, graphite or conductive polymer. The metal can include aluminum(Al), antimony (Sb), bismuth (Bi), boron (B), cadmium (Cd), carbon (C),cerium (Ce), chromium (Cr), cobalt (Co), copper (Cu), dysprosium (Dy),erbium (Er), europium (Eu), gadolinium (Gd), germanium (Ge), gold (Au),graphite (C), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir),iron (Fe), lanthanum (La), lutetium (Lu), magnesium (Mg), manganese(Mn), molybdenum (Mo), neodymium (Nd), nickel (Ni), niobium (Nb),palladium (Pd), platinum (Pt), praseodymium (Pr), rhenium (Re),ruthenium (Ru), samarium (Sm), selenium (Se), scandium (Sc), silver(Ag), silicon (Si), tantalum (Ta), terbium (Tb), thulium (Tm), tin (Sn),titanium (Ti), tungsten (W), vanadium (V), ytterbium (Yb), yttrium (Y),zirconium (Zr) or zinc (Zn), and the metal alloy can include aluminumcopper (AlCu), aluminum chromium (AlCr), aluminum magnesium (AlMg),aluminum silicon (AlSi), aluminum silver (AlAg), cerium gadolinium(CeGd), cerium samarium (CeSm), chromium silicon (CrSi), cobalt chromium(CoCr), cobalt iron (CoFe), cobalt iron boron (CoFeB), copper cobalt(CuCo), copper gallium (CuGa), copper indium (CuIn), copper nickel(CuNi), copper zirconium (CuZr), hafnium iron (HfFe), iron boron (FeB),iron carbon (FeC), iron manganese (FeMn), iridium manganese (IrMn),iridium rhenium (IrRe), indium tin (InSn), molybdenum silicon (MoSi),nickel aluminum (NiAl), nickel chromium (NiCr), nickel chromium silicon(NiCrSi), nickel iron (NiFe), nickel niobium titanium (NiNbTi), nickeltitanium (NiTi), nickel vanadium (NiV), samarium cobalt (SmCo), silvercopper (AgCu), silver tin (AgSn), tantalum aluminum (TaAl), terbiumdysprosium iron (TbDyFe), terbium iron alloy (TbFe), titanium aluminum(TiAl), titanium nickel (TiNi), titanium chromium (TiCr), tungstenrhenium (WRe), tungsten titanium (WTi), zirconium aluminum (ZrAl),zirconium iron (ZrFe), zirconium nickel (ZrNi), zirconium niobium(ZrNb), zirconium titanium (ZrTi), zirconium yttrium (ZrY), zincaluminum (ZnAl) or zinc magnesium (ZnMg).

The nanostructured anode and cathode electrodes can respectively beformed by depositing at least one material directly on the nano-pittedsubstrate. The anode material and/or the cathode material can bedeposited by sputter-coating, chemical vapor deposition or pulsed lasermethod, such as direct current sputter-coating, radio frequencysputter-coating, magnetron sputter-coating or reactive sputter-coating.Further, the anode material and/or the cathode material can be an oxide,polymeric, ceramic, mineral or metallic material. For example, the anodematerial can include carbon, silicon, graphite, a mixed metal oxide,hydroxyapatite, nichrome or graphite, or more particularly, tin oxide(SnO₂), zinc oxide, copper oxide, titanium oxide, titanium dioxide,vanadium pentoxide, magnesium oxide or silicon dioxide. The cathodematerial can be carbon, silicon, graphite, a copper oxide, graphite, alithium-containing oxide, a phosphate, a fluorophosphate, a silicate,tin oxide, zinc oxide, titanium oxide, titanium dioxide, vanadiumpentoxide, magnesium oxide, silicon dioxide, nichrome or hydroxyapatite,or more particularly, lithium cobalt oxide (LiCoO₂), tin oxide (SnO₂),Li₄Ti₅O₁₂, Li₄Ti₅O₁₂, zinc oxide, copper oxide, titanium oxide, titaniumdioxide, vanadium pentoxide, magnesium oxide, silicon dioxide, nichrome,Li₄Ti₅O₁₂, Li₄Ti₅O₁₂, LiNixCO₁ _(_) _(2x)MnO₂, LiNi_(0.5)Mn_(1.5)O₄,Li(Ni_(0.8)CO_(0.15)Al_(0.05))O₂, LiMn₂O₄, iron olivine (LiFePO₄),LiFe_(1-x)MgPO₄, LiMoPO₄, LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃, LiVOPO₄,LiMP₂O₇, LiFe_(1.5)P₂O₇, LiVPO₄F, LiAlPO₄F, Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂,Li₂CoPO₄F, Li₂NiPO₄F, Li₂FeSiO₄, Li₂MnSiO₄ or Li₂VOSiO₄.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an electron microscope photograph of a stage in theprocess of the fabrication of nanobaskets by sputter deposition onporous substrates disclosed herein;

FIG. 2 illustrates a sequential stage in the process subsequent to thatshown in FIG. 1;

FIG. 3 illustrates a partial, sectional view of an electron microscopephotograph of a further subsequent stage of the process;

FIG. 4 illustrates a simplified, diagrammatic view an example of cappedtubes utilizing multiple compositions to create a layered structure inaccordance with an illustrative embodiment of the fabrication ofnanobaskets by sputter deposition on porous substrates disclosed herein;

FIGS. 5, 6 and 7 illustrate subsequent, sequential stages in theformation of capped tubes of multiple compositions shown in FIG. 4;

FIG. 8 illustrates an electron microscope photograph of a sectional viewof a partially capped nanobasket in accordance with an illustrativeembodiment of the fabrication of nanobaskets by sputter deposition onporous substrates disclosed herein;

FIG. 9 illustrates an electron microscope photograph of a cappednanobasket utilizing multiple compositions to create a layered structurein accordance with an illustrative embodiment of the fabrication ofnanobaskets by sputter deposition on porous substrates disclosed herein;

FIGS. 10 through 13 illustrate potential applications of the fabricationof nanobaskets by sputter deposition on porous substrates disclosedherein;

FIG. 14 illustrates a transmission electron microscope photo of thegrains composing the nanobasket in accordance with an illustrativeembodiment of the fabrication of nanobaskets by sputter deposition onporous substrates disclosed herein;

FIG. 15 shows an atomic force microscope (AFM) image of a nano-pittedaluminum surface in accordance with an illustrative embodiment of thenanopatterned substrate that serves as both a current collector andtemplate for nanostructured electrode growth disclosed herein;

FIGS. 16A and 16B show SEM images of 200 nm pits in the nano-pittedaluminum surface shown in FIG. 17;

FIGS. 17A and 17B show SEM images of 400 nm of SnO₂ electrode sputteredover a nano-pitted aluminum substrate in accordance with an illustrativeembodiment of the nanopatterned substrate that serves as both a currentcollector and template for nanostructured electrode growth disclosedherein;

FIGS. 18A through 18D show SEM images of a nano-pitted aluminumsubstrate (top) before and (bottom) after deposition and removal of atin oxide layer, with the pores at the bottom being approximately 20-40nm in diameter;

FIG. 19 illustrates an example of a nano-pitted metal film serving asboth current collector and growth substrate for nanostructuredelectrodes; and

FIG. 20 illustrates and example of nanostructured electrodes grown onthe nano-pitted metal film of FIG. 19 that maintains the nanostructure.

Other advantages and features will be apparent from the followingdescription and from the claims.

DETAILED DESCRIPTION OF THE INVENTION

The invention discussed herein is merely illustrative of specificmanners in which to make and use this invention and are not to beinterpreted as limiting in scope.

While the invention has been described with a certain degree ofparticularity, it is to be noted that many modifications may be made inthe details of the construction and the arrangement of the devices andcomponents without departing from the spirit and scope of thisdisclosure. It is understood that the invention is not limited to theembodiments set forth herein for purposes of exemplification.

Referring to the figures of the drawings, wherein like numerals ofreference designate like elements throughout the several views, andinitially to FIG. 1 illustrating an electron microscope photograph of astage in the process of the formation of a nanostructured electrodesthat includes capped nanotubes, termed “nanobaskets” by asputter-coating method on a porous substrate as the template for thenanostructured electrodes. FIG. 2 illustrates an electron microscopephotograph of approximately 400 nanometers of tin oxide sputtered ontoan alumina substrate. It will be observed that the material is beginningto cap or close over. FIG. 3 illustrates an electron microscopephotograph of a partial cross-section of the photo shown in FIG. 2. Thealumina substrate may be viewed with the tin oxide sputtered thereon toform the nanostructured electrodes. FIG. 8 is an electron microscopephotograph that shows that as the nanostructured electrodes begin to capover, very small nano-channels are formed, which have potentialapplications in the trapping of molecular species, confinement of DNAand RNA, specialized filtrations, and chromatographic analysis. This isan example of a “partially capped” nanostructured electrode. Partiallycapped nanostructured electrodes are created by stopping the sputteringprocess before the walls of the nanostructured electrodes have growntogether to form a continuous cap. FIG. 9 illustrates an electronmicroscope photograph of capped nanostructured electrodes utilizingmultiple compositions to create a layered structure. FIG. 14 shows thenano-grains that compose the walls and cap of the nanostructuredelectrodes. The fact that the nanostructured electrodes contain asubstructure of nano-grains is expected to further enhance theperformance of the nanostructured electrodes. FIGS. 16 through 18 showSEM images of 200 nm pits in a nano-pitted metal substrate and ofnanostructured electrodes grown directly on the substrate.

The nanostructured electrodes can be formed using sputter-coatingtechniques, including but not limited to, DC sputter-coating, RFsputter-coating and RF magnetron sputter-coating. Chemical reactivesputtering could also be used to form the nanostructured electrodes. Inaddition, the nanostructured electrodes could also be formed usingchemical vapor deposition or pulsed laser methods.

At the surface of the nanostructured or nano-pitted substrate, the poreshave a continuous edge, which could be of any relative geometricconfiguration. As a target material is sputter-coated, nanoscaleclusters of the material collect preferentially on the continuous edgeof the pores of the underlying substrate. As the process of depositingmaterial continues, a gradual build-up of “walls” effectively extendsthe pore structure with the target material to form a nanotube. The poresize of these nanotubes is dependent on the substrate's original porestructure and, therefore, their diameter can be varied by usingsubstrates of varying pore sizes.

As the sputter-coating process is continued, the walls grow thicker asthey grow taller so that they will eventually touch, capping over thepore spaces with deposited material to form the base or end of ananostructured electrode. Depending on the parameters used in thesputter-coating process, such as plasma gas concentration, power, targetmaterials, and underlying substrate, the pores can be made to cap atvarious lengths or heights from the substrate surface, ranging from tensto hundreds of nanometers.

The substrate could be made from numerous materials whose surface energyvalues are such that they are conducive to the formation ofnanostructured electrodes. In one example, a substrate has a pluralityof pores that range between ten (10) micrometers to one (1) nanometer(nm) in diameter. Various substrates could be used, e.g., eitherpolymeric (such as polycarbonate), ceramic material (such as aluminaoxide (Al₂O₃)), silicon or metallic porous structures (such as aluminum(Al), antimony (Sb), bismuth (Bi), boron (B), cadmium (Cd), carbon (C),cerium (Ce), chromium (Cr), cobalt (Co), copper (Cu), dysprosium (Dy),erbium (Er), europium (Eu), gadolinium (Gd), germanium (Ge), gold (Au),graphite (C), hafnium (Hf), holmium (Ho), indium (In), iridium (Ir),iron (Fe), lanthanum (La), lutetium (Lu), magnesium (Mg), manganese(Mn), molybdenum (Mo), neodymium (Nd), nickel (Ni), niobium (Nb),palladium (Pd), platinum (Pt), praseodymium (Pr), rhenium (Re),ruthenium (Ru), samarium (Sm), selenium (Se), scandium (Sc), silver(Ag), silicon (Si), tantalum (Ta), terbium (Tb), thulium (Tm), tin (Sn),titanium (Ti), tungsten (W), vanadium (V), ytterbium (Yb), yttrium (Y),zirconium (Zr) or zinc (Zn)), metal alloy porous structures (such asaluminum copper (AlCu), aluminum chromium (AlCr), aluminum magnesium(AlMg), aluminum silicon (AlSi), aluminum silver (AlAg), ceriumgadolinium (CeGd), cerium samarium (CeSm), chromium silicon (CrSi),cobalt chromium (CoCr), cobalt iron (CoFe), cobalt iron boron (CoFeB),copper cobalt (CuCo), copper gallium (CuGa), copper indium (CuIn),copper nickel (CuNi), copper zirconium (CuZr), hafnium iron (HfFe), ironboron (FeB), iron carbon (FeC), iron manganese (FeMn), iridium manganese(IrMn), iridium rhenium (IrRe), indium tin (InSn), molybdenum silicon(MoSi), nickel aluminum (NiAl), nickel chromium (NiCr), nickel chromiumsilicon (NiCrSi), nickel iron (NiFe), nickel niobium titanium (NiNbTi),nickel titanium (NiTi), nickel vanadium (NiV), samarium cobalt (SmCo),silver copper (AgCu), silver tin (AgSn), tantalum aluminum (TaAl),terbium dysprosium iron (TbDyFe), terbium iron alloy (TbFe), titaniumaluminum (TiAl), titanium nickel (TiNi), titanium chromium (TiCr),tungsten rhenium (WRe), tungsten titanium (WTi), zirconium aluminum(ZrAl), zirconium iron (ZrFe), zirconium nickel (ZrNi), zirconiumniobium (ZrNb), zirconium titanium (ZrTi), zirconium yttrium (ZrY), zincaluminum (ZnAl) or zinc magnesium (ZnMg)), among others, could also beused. The nanoporous substrate could be created by laser ablation, achemical etching process, an electrochemical process, track etching,micro- or nano-lithography, contact lithography, X-ray-beam lithography,electron-beam lithography, ion-beam lithography, photo-lithography,nano-imprint lithography, chemical self-assembly or by other methods.

For example, a nanoporous anodized aluminum oxide (AAO) substrate couldbe prepared by applying an electrical potential to an aluminum sheetwhile in an aqueous acid solution and then electro-polishing thesurface. In particular, AAO synthesis is accomplished by assembling anelectrochemical cell with a sheet of polished high-purity aluminum asthe anode, graphite or steel as the counter electrode and an acidicelectrolyte (usually oxalic, phosphoric, or sulfuric acid). When apotential is applied across the cell, aluminum oxide is formed at thesurface of the aluminum sheet, and under certain conditions the oxidelayer forms well-ordered pores in a hexagonal pattern. The poresself-assemble during anodization due to competition between twoprocesses: the formation of alumina at the oxide/aluminum interface, andthe dissolution of the alumina at the oxide/electrolyte interface. Asthe aluminum oxide grows, the aluminum is removed from the aluminumsubstrate leaving a nano-pitted surface having pores that match thearrangement of pores in the oxide layer. The aluminum metal layer isremoved once the oxide has reached the desired thickness. The AAOsubstrate can then be used as a growth template for nanostructuredelectrodes, or as illustrated in FIGS. 19 and 20, the nano-pittedaluminum substrate can directly serve as both the growth template andcurrent collector for the nanostructured electrodes.

The processes and methods disclosed herein are robust and can beutilized with various materials for making the nanostructure electrodes.For example, copper oxide electrodes are of importance in catalyticoperations, while metal alloys, such as nichrome, are useful for themanufacture of thermal devices. Other materials such as hydroxyapatite,the mineral closest in composition to bone, are amenable to thistechnique and have been observed to form nanobaskets. These materialsmay have important applications as bone mimics and tissue scaffolding.In addition, anode materials could be graphite, SnO₂, silicon,Li₄Ti₅O₁₂, Li₄Ti₅O₁₂, or any other suitable anode material. Cathodematerials could include lithium-containing oxides, such as lithiumcobalt oxide (LiCoO₂), mixed metal oxides, such as LiNixCO₁ _(_)_(2x)MnO₂, LiNi_(0.5)Mn_(1.5)O₄, Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂,LiMn₂O₄; phosphates, such as iron olivine (LiFePO₄) and it is variantssuch as LiFe_(1-x)MgPO₄, LiMoPO₄, LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃,LiVOPO₄, LiMP₂O₇, or LiFe_(1.5)P₂O₇; fluorophosphates, such as LiVPO₄F,LiAlPO₄F, Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂, Li₂CoPO₄F, or Li₂NiPO₄F;silicates, such as Li₂FeSiO₄, Li₂MnSiO₄, or Li₂VOSiO₄, or any othersuitable cathode material.

The fabrication processes disclosed herein also allow the formation ofnanostructured electrodes composed of multiple compositions. The abilityto create layered electrodes directly on a nanostructure or nano-pittedmetal substrate allows for the straightforward and easy assembly ofnano-devices using appropriate selections of materials, such as currentcollectors, electrodes, and semiconductors or layered semiconductors. Alayered nanobasket system may made by sputtering a first material, butstopping the sputtering at some desired point before the walls havegrown thick enough to form a cap. A second material can then besputtered atop the first, continuing to extend the walls of the basketsupward. Sputtering of this second material can continue until cappingoccurs, or it can also be stopped at a desired point before the wallshave grown together, and more layers can be added. The number of layerspossible is dependent upon the materials and pore sizes used. Thenanobasket structures and/or layers within them may be made from dopedelements or compounds; for example, SnO₂ doped with Indium.

In addition, a thin layer of liquid electrolyte or a thin layer of solidelectrolyte can be utilized. The liquid electrolyte could be aqueous ornon-aqueous in nature. A solid electrolyte could include oxides,ceramics or polymer electrolytes. The thin layer could be placed on theelectrodes by several methods, including but not limited to DC sputtercoating, RF magnetron sputter coating, vapor deposition, spin coatingand chemical self-assembly to form molecular level layers. Liquids andsolutions could also be placed between the two electrode layers byplacing micro- or nanoparticle insulation spacers between the twoelectrode structures and allowing capillary action to pull the liquidsor solvents between the two electrodes. These spacers could be placed onone or both electrode surfaces, such as by dusting the surface withinsulating micro- or nanoscale particles that would serve as thespacers, and then the two electrodes would be placed together. Dispersedinsulating particles on the electrode surface would prevent the twoelectrodes from making direct contact and would leave a thin continuousvoid that the electrolyte could fill. Exposure of an edge of the twoelectrodes separated by the spacers to a liquid or solution would drawthe liquid or solution into the thin void, thereby filling this spacewith electrolyte. The insulating spacer particles could be dispersed inthe liquid or solution for placement. In this method, the solution orliquid could be placed on the electrode surface by solvent casting, spincoating or other techniques. The two electrodes would be placed togetherwith the solvent and spacers already on one or both electrodes trappingthe electrolyte between the two electrodes. Direct electrode contactwould again be prevented by the spacers on the electrode surface. Theliquid could be any aqueous or non-aqueous electrolyte. The solventcould contain a dissolved polymer and inorganic salts. With thissolution, the solvent maybe evaporated leaving a polymer electrolytebetween the two electrodes.

In whatever means the thin layer of electrolyte is placed or depositedbetween the two electrode surfaces to complete a nanobattery system, theelectrolyte will take advantage of the enhanced surface area of eachelectrode surface. The electrolyte will disperse itself into thefissures and crevices between the nanobasket structure, and onto theroughened nanostructure of the top surface of the nanobaskets takingadvantage of the enhanced electrode surface area.

Example 1

An AAO substrate is placed on the sample stage of an RF-magnetronsputtering system which is fitted with a tin oxide (SnO₂) target. Achamber is filled and flushed with argon gas, and sputtering isinitiated under system conditions of 0.01 mbar argon pressure and 35watts forward power. In accordance with the generally recognizedprinciples of sputter depositions, SnO₂ is removed from the target anddeposited onto the AAO substrate. Film thickness is monitored using aquartz crystal thickness monitor. When the desired thickness is reached,turning off the power halts the sputtering process.

Example 2

An AAO substrate is placed on the sample stage of an RF-magnetronsputtering system which is fitted with a gold (Au) target. The chamberis filled and flushed with argon, and sputtering is initiated undersystem conditions of 0.01 mbar argon pressure and 35 watts forwardpower. In accordance with the generally recognized principles of sputterdepositions, gold is removed from the target and deposited onto the AAOsubstrate. Film thickness is monitored using a quartz crystal thicknessmonitor. When the desired thickness is reached, sputtering is halted andthe chamber is opened. A new target of LiCoO₂ is installed. The chamberis again filled and flushed with argon, and sputtering is initiatedunder system conditions of 0.01 mbar argon pressure and 35 watts forwardpower. LiCoO₂ is removed from the target and deposited onto the goldlayer previously deposited on the AAO substrate. Film thickness ismonitored using a quartz crystal thickness monitor. When the desiredthickness is reached, turning off the power halts the sputteringprocess.

FIGS. 4, 5, 6 and 7 illustrate simplified diagrammatic views of thesequential fabrication of capped nanostructures by sputter depositionutilizing multiple compositions. FIG. 4 illustrates the pores of thesubstrate prior to application of any sputter deposition. FIG. 5illustrates use of sputter deposition techniques to apply a metallicdeposit onto the edges or open ends of the nanotube structures. FIGS. 5,6 and 7 illustrate the sequential application of a metallic oxide ontothe metal layer previously deposited on the nanotube structure.Continued application of the metallic oxide results in the capping overof the tubes.

Example 3

A nanostructured metal substrate was formed by chemical polishing of analuminum film in concentrated phosphoric acid for 5 minutes and thenrinsed. The aluminum film was then placed into electrochemical cell with0.3 M oxalic acid electrolyte solution at near 4° C., and a potential of40 V was applied for 1 hour. The 40 V potential was then decreased insteps of 2 Vmin⁻¹ until the potential reached 2 V. Then, pores werewidened by etching in phosphoric acid to form a nano-pitted aluminumsubstrate that can serve as both a growth template for nanostructuredmaterials and as a current collector for the resulting nanostructuredmaterial.

The potential factors in controlling the dimensions of the pits in thenano-pitted aluminum substrate include oxidation voltage, time ofoxidation, temperature and concentration of the oxalic acid electrolyte,and the electrochemical conditions of the step-down potential oxidelayer dissolution procedure.

The results of the above procedure are shown in FIG. 18. The surface ofthe aluminum foil after polishing is shown for comparison in the toppanes of FIG. 18. After the oxidation and step-down voltage procedure,the sample was etched in phosphoric acid in order to dissolve theremainder of the oxide layer. SEM imagery in the bottom panes of FIG. 18show that the surface of the aluminum is covered with a very regularpattern of pores with diameters ranging from 20 to 40 nm. While this issmaller than the desired pore diameter of 200 nm, a refinement of thisprocedure should produce the desired 200 nm diameter pores.

Example 4

Nanostructured films of tin oxide were deposited directly on nano-pittedaluminum substrates, such as those fabricated above in Example 3, byradio frequency (RF) magnetron sputtering from a SnO₂ target in an argonatmosphere, utilizing a Cressington® 208 sputter coater with Manitou®power source. The pits in the aluminum substrate were approximately 200nm in diameter and approximately 150 nm deep. Sputtering was performedat room temperature under approximately 0.01 mbar of argon pressure,with a spacing of 7 cm between the target and the sample. As can be seenin FIGS. 17 and 18, the growth of SnO₂ columns begins along the edges ofthe pits. The holes in the SnO₂ structures are the bottom of the pits inthe aluminum metal. In these figures, the SnO2 columns have beendeposited by sputtering so that their height from the surface isapproximately 300 nm to approximately 400 nm. Deposition by sputteringmore material will make the columns taller providing more surface areafor applications such as battery electrodes. This nanostructuredelectrode, in this case SnO₂, is directly in contact with the aluminumcurrent collector.

Example 5

The nanostructures disclosed herein can be utilized in photovoltaicdevices 18 as shown in FIG. 10. In typical photovoltaic devices, atransparent current collector must be used so that light may passthrough it for interaction with the photovoltaic material. Using thelayered nanostructure, a photovoltaic 18 could be manufactured by firstdepositing 14 a conducting metal layer 12 on the nanoporous substrate10. This layer will serve as a current collector 12. A second layer of aphotoactive semiconductor (photovoltaic layer) 13 will be deposited andallowed to cap over. The size of the pores in the nanoporous substrate10 can be of the appropriate size to interact with light such that theyfunction as a waveguide. This will facilitate the passage of light 11through to open pores of the non-coated side of the nanoporous substrate10. This light will be able to pass through the pores in the nanoporouscurrent collector 12 impinging on the capped photovoltaic material 13.The size of the pore and the curvature of the cap portion of thenanobaskets could further accentuate the interaction of light by actingboth as an additional waveguide and a lens, further focusing the lighton the photovoltaic material 13 and enhancing performance. The completedphotocell 18 would be constructed by placing an electrolyte 15,complementary electrode 16, and a second current collector 17,respectively on the capped side of the photovoltaic material 13.

Example 6

A multilayered, nanostructured material could also be used to make thinfilm battery systems as shown in FIG. 11. Using the layerednanostructure, a layer of nanobaskets of an appropriate batteryelectrode material 21 is sputter-coated onto a nanoporous substrate 20.The nanoporous substrate 20 and the nanobaskets 21 are filled withelectrolyte 22 using capillary action to “pull” the electrolyte into thepores (as described in Applicant's U.S. Pat. No. 6,586,133, which isincorporated herein by reference in its entirety) or other techniques.The opposite side of the nanoporous substrate 20 would still have poresthat are open, but filled with electrolyte 22. One configuration of thebattery would now cover this end of the substrate with an appropriateelectrode material forming a battery. Placing the electrode 23 on thisside could be done by many methods including sputter-coating, spreadingof pastes of composite electrode materials, etc. A current collector 24would be affixed to this electrode 23. This thin film battery would haveincreased performance because of the increased surface area of thenanobasket electrode and because of the enhanced performance ofelectrolyte materials confined in nanoporous materials.

Example 7

Another battery configuration as depicted in FIG. 12 would include firstplacing a layer of current collecting material 31, such as a metal, bysputter-coating on the nanoporous substrate 30. This current collectinglayer 31 is capped with nanobaskets 33 of an appropriate batteryelectrode material. Using capillary action to “pull” the electrolyteinto the pores, both the pores of the substrate 30 and those in thecurrent collector 31 and the nanobaskets 33 are filled with electrolyte32. The opposite side of the nanoporous substrate would still have poresthat are open, but filled with electrolyte 34. Deposition of thecomplementary electrode 35 would again be done by using sputter-coating.Because of the nanoporous substrate 33, a nanobasket electrode layer 34would be formed. This configuration would benefit from having twoelectrodes 32 and 34 both having a nanobasket configuration. This thinfilm battery would have increased performance because of the increasedsurface area of both of the nanobasket electrodes 32 and 34 and becauseof the enhanced performance of electrolyte materials confined innanoporous materials.

Example 8

As shown in FIG. 13, another configuration would allow the in situformation of a battery anode in a nanostructured thin film battery. Thisconfiguration includes first depositing a first layer of currentcollecting material 41 by sputter-coating on a nanoporous substrate 40.This layer 41 is not allowed to cap. This current collecting layer 41 isthen capped with nanobaskets 42 of an appropriate battery cathodematerial by deposition by sputter-coating. This material must containmetal ions of the same composition of the anode desired to be formed. Byusing capillary action to “pull” the electrolyte into the pores, thepores of the substrate 40 and those in the current collector 41 and thenanobaskets 42 can be filled with electrolyte 43. A second currentcollector 44 would be placed on top of the nanobasket electrode layer42. The opposite side of the nanoporous substrate would still have poresthat are open, but filled with electrolyte 43. At this point a thin filmbattery could be formed by in situ deposition of an anode 45. Thistechnique is applied to the nanostructured system by applying anappropriate current 46 to the two current collectors 41 and 44 drawingmetal ions from the cathode layer 42 and through the electrolyte 43present in the nano-pores. This will result in electrochemical platingof the metal anode 45 onto the current collector 41 that closest to thenanobasket openings. This plated metal would be the anode 45 formed insitu. Since this anode 45 would be in very close proximity to thenanobasket 42, cathode material, it would enhance performance. Since theanode 45 is deposited in situ and is not exposed to air, the anode 45 isless likely to be degraded by air exposure, thus eliminating a majorproblem in the development of thin-film lithium batteries. Once again,this thin film battery would also have increased performance because ofthe increased surface area of the nanobasket electrode and because ofthe enhanced performance of electrolyte materials confined in nanoporousmaterials.

Whereas, the invention has been described in relation to the drawingsand claims, it should be understood that other and furthermodifications, apart from those shown or suggested herein, may be madewithin the scope of the invention.

What is claimed is:
 1. A method of constructing a nanobattery, saidmethod comprising the steps of: a. forming a nanostructured anodeelectrode directly on a nano-pitted anode substrate, wherein saidnano-pitted anode substrate is an oxidized metal thin film configured asboth an anode current collector and an anode growth substrate for saidnanostructured anode electrode, including the step of nano-pitting saidanode substrate through an electrochemical process; b. forming ananostructured cathode electrode directly on a nano-pitted cathodesubstrate, wherein said nano-pitted cathode substrate is an oxidizedmetal thin film configured as both a cathode current collector and acathode growth substrate for said nanostructured cathode electrode,including the step of nano-pitting said cathode substrate through anelectrochemical process; and c. forming an electrolyte layerintermediate of said nanostructured anode cathode and saidnanostructured anode to construct said nanobattery.
 2. The method ofclaim 1 wherein said oxidized metal thin film forming said nano-pittedanode substrate and/or said oxidized metal thin film forming saidnano-pitted cathode substrate is selected from the group consisting ofaluminum (Al), antimony (Sb), bismuth (Bi), boron (B), cadmium (Cd),carbon (C), cerium (Ce), chromium (Cr), cobalt (Co), copper (Cu),dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), germanium(Ge), gold (Au), graphite (C), hafnium (Hf), holmium (Ho), indium (In),iridium (Ir), iron (Fe), lanthanum (La), lutetium (Lu), magnesium (Mg),manganese (Mn), molybdenum (Mo), neodymium (Nd), nickel (Ni), niobium(Nb), palladium (Pd), platinum (Pt), praseodymium (Pr), rhenium (Re),ruthenium (Ru), samarium (Sm), selenium (Se), scandium (Sc), silver(Ag), silicon (Si), tantalum (Ta), terbium (Tb), thulium (Tm), tin (Sn),titanium (Ti), tungsten (W), vanadium (V), ytterbium (Yb), yttrium (Y),zirconium (Zr) or zinc (Zn).
 3. The method of claim 1 wherein saidoxidized metal thin film forming said nano-pitted anode substrate and/orsaid oxidized metal thin film forming said nano-pitted cathode substrateis selected from the group consisting of aluminum copper (AlCu),aluminum chromium (AlCr), aluminum magnesium (AlMg), aluminum silicon(AlSi), aluminum silver (AlAg), cerium gadolinium (CeGd), ceriumsamarium (CeSm), chromium silicon (CrSi), cobalt chromium (CoCr), cobaltiron (CoFe), cobalt iron boron (CoFeB), copper cobalt (CuCo), coppergallium (CuGa), copper indium (CuIn), copper nickel (CuNi), copperzirconium (CuZr), hafnium iron (HfFe), iron boron (FeB), iron carbon(FeC), iron manganese (FeMn), iridium manganese (IrMn), iridium rhenium(IrRe), indium tin (InSn), molybdenum silicon (MoSi), nickel aluminum(NiAl), nickel chromium (NiCr), nickel chromium silicon (NiCrSi), nickeliron (NiFe), nickel niobium titanium (NiNbTi), nickel titanium (NiTi),nickel vanadium (NiV), samarium cobalt (SmCo), silver copper (AgCu),silver tin (AgSn), tantalum aluminum (TaAl), terbium dysprosium iron(TbDyFe), terbium iron alloy (TbFe), titanium aluminum (TiAl), titaniumnickel (TiNi), titanium chromium (TiCr), tungsten rhenium (WRe),tungsten titanium (WTi), zirconium aluminum (ZrAl), zirconium iron(ZrFe), zirconium nickel (ZrNi), zirconium niobium (ZrNb), zirconiumtitanium (ZrTi), zirconium yttrium (ZrY), zinc aluminum (ZnAl) or zincmagnesium (ZnMg).
 4. The method of claim 1 wherein said step of formingsaid nanostructured anode electrode further comprises the step ofdepositing at least one anode material directly on said oxidized metalthin film forming said nano-pitted anode substrate and/or wherein saidstep of forming said nanostructured cathode electrode further comprisesthe step of depositing at least one cathode material directly on saidoxidized metal thin film forming said nano-pitted cathode substrate. 5.The method of claim 4 wherein said step of depositing said anodematerial and/or said step of depositing said cathode material isaccomplished by sputter-coating, chemical vapor deposition or pulsedlaser method.
 6. The method of claim 5 wherein said sputter-coating isselected from the group consisting of direct current sputter-coating,radio frequency sputter-coating, magnetron sputter-coating or reactivesputter-coating.
 7. The method of claim 4 wherein said anode materialand/or said cathode material is selected from the group consisting ofconductive materials consisting of an oxide, polymeric, ceramic, mineralor metallic material.
 8. The method of claim 7 wherein said anodematerial is selected from the group consisting of carbon, silicon,graphite, a mixed metal oxide, hydroxyapatite, nichrome or graphite. 9.The method of claim 7 wherein said anode material further comprises tinoxide (SnO₂), zinc oxide, copper oxide, titanium oxide, titaniumdioxide, vanadium pentoxide, magnesium oxide or silicon dioxide.
 10. Themethod of claim 7 wherein said cathode material is selected from thegroup consisting of carbon, silicon, graphite, a copper oxide, graphite,a lithium-containing oxide, a phosphate, a fluorophosphate, a silicate,tin oxide, zinc oxide, titanium oxide, titanium dioxide, vanadiumpentoxide, magnesium oxide, silicon dioxide, nichrome or hydroxyapatite.11. The method of claim 7 wherein said cathode material furthercomprises lithium cobalt oxide (LiCoO₂), tin oxide (SnO₂), Li₄Ti₅O₁₂,Li₄Ti₅O₁₂, zinc oxide, copper oxide, titanium oxide, titanium dioxide,vanadium pentoxide, magnesium oxide, silicon dioxide, nichrome,Li₄Ti₅O₁₂, Li₄Ti₅O₁₂, LiNixCO₁ _(_) _(2x)MnO₂, LiNi_(0.5)Mn_(1.5)O₄,Li(Ni_(0.8)Co_(0.15)Al_(0.05))O₂, LiMn₂O₄, iron olivine (LiFePO₄),LiFe_(1-x)MgPO₄, LiMoPO₄, LiCoPO₄, LiNiPO₄, Li₃V₂(PO₄)₃, LiVOPO₄,LiMP₂O₇, LiFe_(1.5)P₂O₇, LiVPO₄F, LiAlPO₄F, Li₅V(PO₄)₂F₂, Li₅Cr(PO₄)₂F₂,Li₂CoPO₄F, Li₂NiPO₄F, Li₂FeSiO₄, Li₂MnSiO₄ or Li₂VOSiO₄.
 12. The methodof claim 1 further comprising the steps of: a. chemically polishing ametal thin film in a first acid for a predetermined amount of polishingtime; b. oxidizing said metal thin film with an acidic solution in anelectrochemical cell at a predetermined temperature, a firstpredetermined voltage potential and for a predetermined amount ofoxidation time; c. decreasing said first predetermined voltage potentialat a predetermined step-down rate to a second predetermined voltagepotential; and d. etching said oxidized metal thin film with a secondacid to form said anode nano-pitted substrate and/or said cathodenano-pitted substrate.
 13. The method of claim 1 wherein each of saidnano-pits of said nano-pitted anode substrate and said nano-pittedcathode substrate has a diameter of up to about 200 nanometers and adepth of up to about 150 nanometers.